1. Field of the Invention
The present invention relates to a vacuum pump component, a Siegbahn type exhaust mechanism, and a compound vacuum pump. More particularly, the present invention relates to a vacuum pump component and a Siegbahn type exhaust mechanism effectively connecting conduits each having an exhausting function in a vacuum pump, in which the vacuum pump component or the Siegbahn type exhaust mechanism is disposed, and a compound vacuum pump, which effectively connects conduits each having an exhausting function.
2. Description of the Related Art
A vacuum pump includes a casing forming an outer casing including an inlet port and an outlet port. In the casing, a structure which causes the vacuum pump to perform an exhausting function is contained. The structure which causes the vacuum pump to perform the exhausting function mainly includes a rotary portion (rotor portion) that is rotatably pivoted and a stationary portion (stator portion) that is fixed to the casing.
In addition, a motor for rotating a rotary shaft at a high speed is provided. When the rotary shaft is rotated at a high speed by the operation of the motor, gas is sucked in through the inlet port by the interaction of a rotor vane (rotary disk) and a stator vane (stationary disk) and exhausted through the outlet port.
Among vacuum pumps, a Siegbahn type molecular pump having a Siegbahn type configuration includes a rotary disk (rotary disc) and a stationary disk which is disposed to have a gap (clearance) with the rotary disk in an axial direction. In a surface of at least one of the rotary disk and the stationary disk which faces the gap, spiral groove (referred to also as helical groove) flow paths have been engraved. The Siegbahn type molecular pump is the vacuum pump in which the rotary disk gives a momentum in a direction tangential to the rotary disk (i.e., direction tangential to the rotating direction of the rotary disk) to gas molecules that have dispersedly entered the spiral groove flow paths. Thus, using the spiral grooves, the vacuum pump gives a dominant directionality from an inlet port toward an outlet port to the gas to exhaust the gas.
To industrially use such a Siegbahn type molecular pump or a vacuum pump having a Siegbahn type molecular pump portion, the rotary disks and the stationary disks are provided in a multi-stage configuration. This is because, when the rotary disk and the stationary disk are provided in a single stage, a compression ratio is insufficient.
Note that the Siegbahn type molecular pump is a radial flow pump element. To provide a multi-stage Siegbahn type molecular pump, a configuration is needed which exhausts gas from an inlet port to an outlet port (i.e., in the axial direction of a vacuum pump) by folding back a flow path at the outer peripheral end portions and the inner peripheral end portions of the rotary disks and the stationary disks. In the configuration, the gas is exhausted such that, e.g., after exhausted from the outer peripheral portion to the inner peripheral portion, the gas is exhausted from the inner peripheral portion to the outer peripheral portion, and then the gas is exhausted again from the outer peripheral portion to the inner peripheral portion.
Japanese Patent Application Publication No. (S) 60-204997 describes a technique in which, in a pump housing, a vacuum pump includes a turbo molecular pump portion, a spiral groove pump portion, and a centrifugal pump portion.
Japanese Utility Model Registration No. 2501275 describes a technique in which, in a Siegbahn type molecular pump, spiral grooves extending in different directions are provided in respective facing surfaces of each of rotary disks and stationary disks.
In each of the related-art configurations described above, gas molecules (gas) flow as follows.
The gas molecules transported to an inner-diameter portion of an upstream Siegbahn type molecular pump portion are exhausted into a space formed between a rotary cylinder and the stationary disk. Then, the gas molecules are attracted by suction by an inner-diameter portion of a downstream Siegbahn type molecular pump portion which is open to the space and transported to an outer-diameter portion of the downstream Siegbahn type molecular pump portion. When a multi-stage configuration is used, the flow is repeatedly observed in each of multiple stages.
However, the space (i.e., the space formed between the rotary cylinder and the stationary disk) described above has no exhausting function. Accordingly, the momentum in an exhaust direction that had been given to the gas molecules by the upstream Siegbahn type molecular pump portion was lost when the gas molecules reached the space.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.